Applicants own Swedish patent SE-0300784-6 (publication number 526 366) discloses and claims through-connections (also referred to as vias) made in a wafer material from the native wafer itself. The vias thereby comprises the same material as the remainder of the wafer and will thus be capable of being processed in a more versatile manner, as describe in detail in said patent, the disclosure of which is incorporated herein in its entirety by reference.
However, for certain applications the resistivity that is attainable in these prior art vias may be too high, and it would be desirable to provide vias with very low resistivity.
It is known to provide vias made of metal, but the conventional methods used (sputtering, plating, or evaporation methods) are all suffering from the problem that it is difficult to fill very small holes with them. Metal vias only allows via last processes (e.g. CMOS structures must be made before via formation).
A general problem addressed in WO2007/089207 is that on one hand it is desirable to have substrates (wafers) having low resistivtiy electrical through-connections (vias). This requires that the starting substrate for making the vias exhibits a low resistivity, e.g. it is highly doped.
On the other hand electronic circuits are made in high resistivity materials (such as non-doped silicon). It is desirable to connect the circuits made on one side of a wafer with structures on the other side using vias of the type mentioned.
These two requirements and preconditions are contradictory. The invention according to WO2007/089207 provides methods for solving this problem.
In U.S. Pat. No. 6,373,097 there is disclosed a field-effect-controllable vertical semiconductor component, and a method for producing the same. The component includes a semiconductor body having at least one drain region of a first conduction type, at least one source region of the first conduction type, at least one body region of a second conduction type between the drain regions and the source regions, and at least one gate electrode insulated from the entire semiconductor body by a gate oxide. A gate terminal and a drain terminal are located on a front side of the wafer, and a source terminal is located on a rear side of the wafer. A monolithically integrated half bridge with a low-side switch and a high-side switch includes the field-effect-controllable vertical semiconductor component and a conventional field-effect-controllable vertical semiconductor component.